Magnetic actuator

ABSTRACT

A magnetic actuator, such as is frequently used to control the operation of electrical contacts of electromagnetic relays. The actuator has a pair of permanent magnets which retain a symmetrically-shaped armature in either of two alternative operating positions. An electromagnet is employed to aid the magnetic flux of one of the permanent magnets and to counteract the magnetic flux of the other in determining the position of the bi-stable armature. A common piece or pole is provided for the several permanent magnet circuits, which pole piece can be adjusted with respect to the armature with equal effect upon the flux flow therein.

United States Patent Garratt et al.

[451 June 27, 1972 MAGNETIC ACTUATOR [72] Inventors: Joseph A. Garrett, Orange; Leonard P.

Ash, Anaheim, both of Calif.

[73] Assignee: Babcock Electronics Corporation, Costa Mesa, Calif.

[22] Filed: May 13, 1971 [21] Appl. No.: 142,883

[52] U.S. CL. ..335/234, 335/237 [51] Int. Cl. ..H01f 7/08 [58] Field of Search ..335/229, 230, 234, 237, 274

[5 6] References Cited UNITED STATES PATENTS 2,941,130 6/1960 Fischer et a1. ..335/230 3,543,203 1 l/l970 Alletru ..335/229 3,544,935 12/1970 Sterff ..335/229 3,585,547 6/1971 Sturman etal ..335/230X Primary Examiner-George Harris Attorney-Nienow & Frater [57] ABSTRACT A magnetic actuator, such as is frequently used to control the operation of electrical contacts of electromagnetic relays. The actuator has a pair of permanent magnets which retain a symmetrically-shaped armature in either of two alternative operating positions. An electromagnet is employed to aid the magnetic flux of one of the permanent magnets and to counteract the magnetic flux of the other in determining the positionof the bi-stable armature. A common piece or pole is provided for the several permanent magnet circuits, which pole piece can be adjusted with respect to the armature with equal effect upon the flux flow therein.

12 Chins, 5 Drawing Figures MAGNETIC ACTUATOR The present invention relates generally to magnetic actuators and, more particularly, to such actuators as are found in electromagnetic relays.

As with most electrical and electronic components, the past several decades have seen many refinements and advances in the construction and operation of electrical switches. They are usually referred to as relays, and employ permanent magnets or electromagnets or combinations thereof for positioning the electrical contacts in accordance with predetermined conditions.

Certain relays are provided with an armature, which controls the position of the electrical contacts, the latter being biased to a given position by suitable mechanical spring means to urge said contacts to a first position. An electromagnet is employed to move said armature and hence said contacts to a second position in response to energization of said electromagnet. Thus, when the relay is energized, the contacts are moved from one position to another, against the force of the biasing means and upon de-energization, the spring means is permitted to return the armature and contacts to their original positions.

For certain applications, it is desirable to have a relay which is bi-stable, namely, one wherein the contacts are held in either of two alternative positions by means of electromagnetic force, there being no need for mechanical biasing means against which the magnetic force operates. Thus, the contacts remain in a first position, under the influence of magnetic force, and so remain until a specific function is performed. Upon reversing the magnetic effect upon the armature, it and the associated contacts are actuated to the second position, in which position they will remain until the conditions are reversed.

It has been the feeling in the industry for a considerable period of time that it would be highly advantageous to have a bi-stable relay which is more compact so as to occupy a small space without closing any of the operating or functional advantages. Also, it is believed desirable to have such a relay which is adjustable so that maximum advantage can be made of the characteristics of the various parts, particularly, the magnetic elements themselves.

Accordingly, it is an object of the present invention to provide a magnetic actuator wherein permanent magnets are em ployed and the magnetic strengths thereof are utilized to maximum advantage.

Another object of the present invention is to provide a magnetic actuator as characterized above, having certain adjustment features which enable the permanent magnets to be used advantageously within predetermined magnetic circuits.

A still further object of the present invention is to provide a magnetic actuator as characterized above, wherein several permanent magnets are employed, each of which has its own magnetic circuit, but wherein there is a common pole piece which can be adjusted to provide like effect to the several magnetic circuits.

An even further object of the present invention is to provide a magnetic actuator as characterized above, which is usable in a bi-stable relay, and wherein the components are symmetrically arranged to provide substantially complete correspondence between the two operating sides of the bi-stable configuration.

Another object of the present invention is to provide a magnetic actuator as characterized above, which is simple and inexpensive to manufacture, and which is rugged and dependable in operation.

The novel features which we consider characteristic of our invention are set forth with particularity in the appended claims.

The device itself, however, both as to its organization and mode of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments, when read in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of an actuator according to the present invention;

FIG. 2 is a sectional view through such actuator, taken substantially along line 2-2 of FIG. 1;

FIG. 3 is a generally horizontal sectional view, taken substantially along line 3-3 of FIG. 1;

FIG. 4 is a side elevational view showing the actuator parts in a given position; and

FIG. 5 is a similar elevational view showing the component parts in adjusted position.

Like reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to FIG. 1 of the drawings, there is shown therein, a magnetic actuator 10 made in accordance with the present invention. Although such actuator is shown throughout the drawings with only a minimal number of parts, it is realized that to utilize the subject actuator in a relay or the like, other additional components would be necessary. The actuator 10 is shown in this simple form, merely to better illustrate the basic principles and advantages of the subject invention which principles and advantages reside in the magnetic actuator itself.

As shown most clearly in FIGS. 1, 4, and 5, there is provided in actuator 10, armature 12 which may take any one of a variety of different forms and shapes. However, a basic, fundamental characteristic of such armature is that it is symmetrical about a central plane or axis so that it has equal operational characteristics in the bi-stable actuator configuration contemplated by the present invention. As such, the armature 12 has an armature portion I4 and a corresponding but opposite armature portion 16, as well as means such as mounting tab 18 which is formed with a pivot hole 18a. As will be readily understood by those persons skilled in the art, the pivot hole is to accommodate a pivot pin or shaft (not shown), whereby the armature 12 is afiorded to pivotal movement between its several positions as will hereinafter be explained. A similar mounting tab 18 is provided at the opposite end of armature 12 to provide longitudinal stability.

Positioned for cooperation with armature portion 14 is a stationary L-shaped pole piece 20. Such pole piece, as shown in FIG. 1 is made to extend the longitudinal length of armature 12.

In like fashion, an L-shaped stationary pole piece 22 is provided for cooperation with armature portion 16 of armature l2.

Positioned on top of the stationary pole pieces 20 and 22 is a support 24 which carries an adjustable pole piece 26, the latter of which is generally U-shaped as shown in FIGS. 1, 4, and 5 of the drawings. Support 24 and pole piece 26 do not extend the length of armature l2 and pole pieces 20 and 22 (as shown in FIGS. 1 and 3) but rather extend for only a portion of such length. The pole piece 26 is firmly secured to the undersurface of support 24 as by any appropriate means, but support 24 is not secured to stationary pole pieces 20 and 22 for purposes of adjustment to be hereinafter described.

As shown most clearly in FIGS. 1, 3, 4, and 5, there is positioned between stationary pole piece 20 and adjustable pole piece 26, a permanent magnet 28. In like fashion, a permanent magnet 30 is positioned between stationary pole piece 22 and the same adjustalbe pole piece 26. In fact, it is desirable to have a sliding fit between pole piece 26 and the permanent magnets 28 and 30 to ensure good magnetic flux conductivity therebetween.

As shown most clearly in FIG. 3 of the drawings, the permanent magnet section of the actuator is shown generally at 32 and covers slightly less than one-half the length of the stationary pole pieces 20 and 22.

In the remaining half of the actuator space, there is provided an electromagnetic operator 34 having a centrally located magnetic core 36 which extends between the core pieces 20 and 22 and about which is wound a suitable electromagnetic winding 38. Lead wires 40 are provided from winding 38 to afford connection to a suitable source of electrical power.

As shown most clearly in FIG. 5 of the drawings, spacers or shims 42 and 44 are provided between the support member 24 and the upper end portions of stationary pole pieces 20 and 22.

The magnetic actuator of the subject invention operates generally as follows:

The permanent magnet 28 is so magnetized and positioned in actuator that magnetic flux is caused to follow a path as shown by the broken line 46. That is, the magnetic lines of force extend from magnet 28 through adjustable pole piece 26, across the air gap between such pole piece and armature 12, through armature portion 14, across the air gap between such armature portion and stationary pole piece 20, and through the latter pole piece to permanent magnet 28.

The permanent magnet 30 is so magnetized and positioned that its flux or lines of force follow a path from magnet 30, through adjustable pole piece 26, across the air gap between said pole piece and armature 12, through armature portion 16, across the air gap between said armature portion and pole piece 22, and through said pole piece 22 to the permanent magnet 30.

With the armature 12 positioned as shown in FIG. 5, the magnetic force of the permanent magnets 20 and 30 exerts a stronger force on armature portion 16 than on armature portion 14. Without the winding 38 of electromagnet 34 energized, the path 48 of permanent 30 is strong in holding armature portion 16 against stationary pole piece 22. In addition thereto, there is a secondary path for the flux from permanent magnet 28 which also holds armature portion 16 against pole piece 22. This latter path results from the large air gap between armature portion 14 and pole piece 20, thus diverting the flux from permanent magnet 28 to a path which includes pole piece 26, the air gap between said pole piece and armature 12, armature portion 16, stationary pole piece 22 and a return circuit through support 24 to stationary pole piece 20 and the opposite side of permanent magnet 28. Thus, the primary path for permanent magnet 30 and the secondary path for permanent magnet 28 cooperate in retaining armature 12 in its position shown in FIG. 5.

Upon energization of winding 38, magnetic lines of force follow a path from core 36 of electromagnet 34, through stationary pole piece 22, across the air gap between said pole piece and armature portion 16, through armature 12, across the air gap between armature portion 14 and pole piece 20, through the latter pole piece to core 36. This causes the magnetic force between the armature portion 14 and pole piece 20 to increase and the magnetic force between portion 16 and pole 22 to decrease. This is because of the overpowering strength of the flux from the electromagnet. As a result, the armature 12 pivots in a clockwise direction as viewed in FIG. 5. This causes armature portion 14 to engage pole piece 20, and thus the contacts or other movable parts associated with said armature are moved to their other positions.

When armature portion 14 approaches stationary pole piece 20, the magnetic flux from permanent magnets 28 and 30 aid in moving armature 14 into such position and in holding it there. The flux from permanent magnet 28 follows its primary path shown in dotted lines at 46, and the flux from permanent magnet 30 follows its secondary path which includes armature portion 14. Thus, if the flux from electromagnet 36 is terminated, the armature will continue to remain in such position that its armature portion 14 is in engagement with sta tionary pole piece 20.

As will be readily realized, by reversing the polarity of energization of electromagnetic winding 34, the direction of flux flow caused by such electromagnet is reversed, thereby causing the magnetic pull on armature portion 16 to be increased and the magnetic pull on armature portion 14 to be decreased. In such event, the armature 12 is caused to pivot in a counterclockwise direction, back to its initial position as shown in FIG. 5.

The present invention permits the armature 12 to be biased to one of its positions of engagement with stationary pole piece 20 or 22, depending upon the relative magnetic strengths of the permanent magnet 28 and 30. That is, in the event it is desired to have armature 12 biased to one or the other of its said positions, it is merely necessary to make the appropriate one of the permanent magnets stronger than the other so that when the electromagnetic force is removed the dominant permanent magnet will return the armature to its preselected position wherein the primary flux path of said dominant permanent magnet is employed.

In such event, the permanent magnets cooperate to retain the armature in either of its two positions depending upon the biasing strength or the use of the electromagnetic flux, but whenever the permanent magnets are the sole strength for locating the armature, it is positioned in accordance with the strongest permanent magnet.

in manufacturing and assembling electromagnetic actuators, particularly those used in relays having electrical contacts, it is frequently necessary to adjust the amount of permanent magnetic force applied to the armature for optimum operation. A most unsatisfactory procedure has heretofore been followed whereby the permanent magnets are, through trial and error demagnetized the proper amount. That is, the prior procedure was to assemble the entire actuator and then remove the permanent magnets and demagnetize them in successive steps until the proper amount of magnetic force was obtained.

This is particularly undesirable when it is realized that permanent magnets have an optimum operating range wherein they are most stable, least influenced by outside effects and generally operate for longer periods of time.

in view of the aforedescribed shortcomings, the present invention provides for adjustment of the pole piece 26. The permanent magnets 28 and 30 are made so that they operate at the most efficient point or range of the magnetization curve. This ensures that said magnets are in their optimum operating condition. Then to properly control the force of such magnets as applied to the armature 12, the adjustable pole piece 26 is moved away from or toward the armature until the air gap therebetween is such that the magnetic force is applied to the armature. At that time, the shims or spacers 42 and 44 are put in place and the entire assembly is firmly fastened together.

Although I have shown and described certain specific embodiments of my invention, 1 am well aware that many modifications thereof are possible.

We claim:

1. A magnetic actuator comprising in combination, a substantially symmetrical pivotal armature, a pair of magnetic pole pieces positioned substantially equidistant from the pivot axis of said armature on opposite sides thereof, a permanent magnet for each of said pole pieces, a selectively energizable electromagnet operable between said pole pieces, and an adjustable center pole forming a portion of the magnetic circuit of each of said permanent magnets in close proximity to the pivot axis of said armature.

2. A magnetic actuator according to claim 1 wherein said center pole is adjustably movable relative to said armature but with equal effect on the magnetic circuits of both of said permanent magnets.

3. A magnetic actuator according to claim 1 wherein said armature is formed with a pair of arms which extend oppositely of and normal to the pivot axis thereof to form a substantially symmetrical armature.

4. A magnetic actuator according to claim 3 wherein said pole pieces are positioned generally on opposite sides of said pivot axis but to one side of said armature for engagement alternatively by the respective arms of said armature.

5. A magnetic actuator according to claim 4 wherein both of said permanent magnets are between said pole pieces but with each such magnet in magnetic flux conducting relation to only its respective pole pieces.

6. A magnetic actuator according to claim 5 wherein said electromagnet is operatively positioned between said pole pieces in flux conducting relation with both of said pole pieces.

7. A magnetic actuator according to claim 6 wherein said center pole is between said permanent magnets in flux conducting relation with each of them and is adjustably movable toward and away from said armature at its pivot axis to thereby vary equally the magnetic paths of said permanent magnets through both of the arms of said armature.

8. A magnetic actuator according to claim 7 wherein means is provided for securing said center pole in adjusted position relative to said armature to provide a predetermined air gap in the magnetic path of each of said permanent magnets.

9. A magnetic actuator according to claim 7 wherein said pole pieces, permanent magnets and center pole are aligned substantially normal to the pivot axis of said armature and to one side thereof such that the only air gaps in the circuit of each permanent magnet with its respective arm of said armature is between said arm and center pole and between said arm and respective pole piece.

10. A magnetic actuator according to claim 9 wherein said actuator is substantially symmetrical about a line through said armature pivot axis and the center of said center pole.

11. A magnetic actuator according to claim 1 wherein said permanent .magnets have different magnetic flux strengths to effectively bias said armature to one of its positions adjacent the appropriate one of said magnetic pole pieces.

12. A magnetic actuator according to claim 10 wherein said permanent magnets have different magnetic flux strengths to efiectively bias said armature to one of its positions adjacent the appropriate one of said magnetic pole pieces. 

1. A magnetic actuator comprising in combination, a substantially symmetrical pivotal armature, a pair of magnetic pole pieces positioned substantially equidistant from the pivot axis of said armature on opposIte sides thereof, a permanent magnet for each of said pole pieces, a selectively energizable electromagnet operable between said pole pieces, and an adjustable center pole forming a portion of the magnetic circuit of each of said permanent magnets in close proximity to the pivot axis of said armature.
 2. A magnetic actuator according to claim 1 wherein said center pole is adjustably movable relative to said armature but with equal effect on the magnetic circuits of both of said permanent magnets.
 3. A magnetic actuator according to claim 1 wherein said armature is formed with a pair of arms which extend oppositely of and normal to the pivot axis thereof to form a substantially symmetrical armature.
 4. A magnetic actuator according to claim 3 wherein said pole pieces are positioned generally on opposite sides of said pivot axis but to one side of said armature for engagement alternatively by the respective arms of said armature.
 5. A magnetic actuator according to claim 4 wherein both of said permanent magnets are between said pole pieces but with each such magnet in magnetic flux conducting relation to only its respective pole pieces.
 6. A magnetic actuator according to claim 5 wherein said electromagnet is operatively positioned between said pole pieces in flux conducting relation with both of said pole pieces.
 7. A magnetic actuator according to claim 6 wherein said center pole is between said permanent magnets in flux conducting relation with each of them and is adjustably movable toward and away from said armature at its pivot axis to thereby vary equally the magnetic paths of said permanent magnets through both of the arms of said armature.
 8. A magnetic actuator according to claim 7 wherein means is provided for securing said center pole in adjusted position relative to said armature to provide a predetermined air gap in the magnetic path of each of said permanent magnets.
 9. A magnetic actuator according to claim 7 wherein said pole pieces, permanent magnets and center pole are aligned substantially normal to the pivot axis of said armature and to one side thereof such that the only air gaps in the circuit of each permanent magnet with its respective arm of said armature is between said arm and center pole and between said arm and respective pole piece.
 10. A magnetic actuator according to claim 9 wherein said actuator is substantially symmetrical about a line through said armature pivot axis and the center of said center pole.
 11. A magnetic actuator according to claim 1 wherein said permanent magnets have different magnetic flux strengths to effectively bias said armature to one of its positions adjacent the appropriate one of said magnetic pole pieces.
 12. A magnetic actuator according to claim 10 wherein said permanent magnets have different magnetic flux strengths to effectively bias said armature to one of its positions adjacent the appropriate one of said magnetic pole pieces. 